1. Field of the Invention
The present invention relates to an electric device, and a method and a computer program product for controlling power supply in an electric device.
2. Description of the Related Art
In recent years, an image forming apparatus, such as a multi-function printer (MFP) having functions of a scanner, a printer, a facsimile machine, etc. and a laser printer (LP), has been in widespread use. One of the ways to improve convenience of the MPF and the like is a reduction of the start-up time. The start-up time is determined by the time taken for a fixing unit to be ready for operation. There is disclosed a technology for switching a fixing control unit for controlling the operation of a fixing unit in the transition from a power-saving mode to a normal operation mode and in the normal operation mode in order to reduce the time taken for the fixing unit to be ready for operation (for example, see Japanese Patent Application Laid-open No. 2002-268441).
While the time taken for a fixing unit to be ready for operation has been reduced with the advance in technology of the fixing unit as described above, there is a case where, due to the enlarged size of software in a controller unit for controlling an image forming apparatus, the start-up time of the image forming apparatus, such as an MFP, is determined by a factor of the controller unit. Accordingly a problem on the side of the controller unit has been recognized.
To solve the above problem, there has been developed a technology for reducing the start-up time in such a manner that a dynamic random access memory (DRAM) in which a program is decompressed, and the decompressed program is constantly supplied with electric power so as to return from STR (Suspend To RAM) each time.
To keep an image forming apparatus, such as an MFP, in a standby state, in most cases, the main power of the image forming apparatus is to be turned on, for example, immediately after a user comes into office in the morning. A recently-popularized image forming apparatus, such as an MFP, contains functionally-different units for achieving a plurality of functions; when the main power of the image forming apparatus is turned on, in most cases, electric power is once distributed to all blocks including a unit that consumes a large amount of electric power in the image forming apparatus, such as an image forming unit. If there is no print request or operation input for more than a certain period of time, the control to make the transition to a power-saving mode is generally performed automatically by a timer contained in the image forming apparatus or manually by a user's operation input.
However, there is a problem that if the image forming apparatus is not used until the image forming apparatus makes the transition to the power-saving mode, electric power for going into a normal operation mode once at start-up (referred to as “initial start-up power”) goes to waste. It is known that much power is consumed especially by a fixing unit in an electrophotographic image forming in the image forming apparatus; therefore, from a standpoint of the demand for environment-friendliness and power conservation of the MFP and the like, it is important to eliminate the initial start-up power.
To solve the problem mentioned above, there is disclosed a technology for setting either to start up an image forming apparatus in a normal operation mode or to make the transition to a power-saving mode immediately after the start-up of the image forming apparatus (for example, see Japanese Patent Application Laid-open No. 2004-230605).
In the technology disclosed in Japanese Patent Application Laid-open No. 2004-230605, either to start up the image forming apparatus in the normal operation mode or to make the transition to the power-saving mode immediately after the start-up is determined on the basis of a history of use of the image forming apparatus, such as the number of times of the transition to the power-saving mode or a printing frequency. However, this determination method does not respond to all situations. For example, even when the image forming apparatus is powered on and started up in the normal operation mode on the basis of its history of use, if the image forming apparatus is not used for a certain period of time, initial start-up power may result in a waste. Furthermore, in Japanese Patent Application Laid-open No. 2004-230605, the settings of the image forming apparatus at the time of initial arrival are not mentioned; if the image forming apparatus is set to be started up in the normal operation mode when the image forming apparatus is initially powered on, and the image forming apparatus is not used for a while at first, initial start-up power may result in a waste.
Moreover, in returning from the power-saving mode due to a job request, i.e., when electric power is distributed to each unit to decompress a program, as described above, it takes time to initialize each unit, to perform a start-up process such as decompression of a program, and to execute the program, so that a user may have to wait for the execution of a job until the image forming apparatus is ready for operation. This is a serious matter especially in fax transmission; at the receipt of a fax, if electric power is to be supplied to a fax unit after the initial call-in, and a program is to be decompressed, and then the fax unit is to receive the fax, the communication latency on the fax sending side is increased, which may result in an increase in communication cost.